Hillclimbing on frozen sand. I was plowing my way up, and I heard a Ping! from the back and backed down. Everything seemed fine, but while I had it up on the lift today, I noticed that the driveshaft can rotate without the axels turning.

 

This was a good diff, and I just changed the fluid a month ago.

It's good I have a 3rd spare in the shed.

A broken stub axle will do the same thing.

Wow. That's the first time I've heard of that happening. I was just telling my brother that it would be almost impossible to blow an open diff. And that I have never heard of it before. But what do ya know...

Have you looked to see if one of your axles busted. I've seen them break at the joint and still stay inside the boot, looking like they were intact.

i second that, check your stub axles that go inside your diff. ( i know when my stub axles break they don't appear to be just by looking at them and i've broke 2 so far , :-\, one on each side . plus i always needed help getting out of the hole or the rest of the way up a steep climb afterwards. ) or your axle shafts.

 

i have never heard of breaking and open diff, atleast not on a subaru. a friend of mine blew out his spider gears on his front axle on his dodge power wagon mid-late 70's, had to dig him out of the snow he was stuck in a 4' ditch. that was a fun night spent 3hrs getting him out.

I can say that it's deffiniately not the stub shafts or the axels because you can get the diff to engage if you rotate a wheel and the input shaft at the same time, it will catch in and work for a bit, then go free. I'd say it was the ring gear, but... it might also be the bearing for the pinion shaft letting the pinion skip out of the ring gear.

 

When you put it in 4wd, and take a corner, it'll bind up like normal and then whabam! unload as the diff skips.

 

The last diff I grenaded was an open one, but i was doing some nice posi-style burnouts and had some wheel hop happen. That one the crosspin broke and the carrier cracked and the spyder gears shattered and jammed in the ring gear.. it was ugly.

 

What's a pain is that i couldn't get the roll pins in right last time, so I just hammered one in from each side of the axels. I was in a hurry to get some wheel drive back, and I figured I wouldn't blow this diff because I was done doing burnouts with the big tires on. I'll have to drill the rollpins out.

 

I'll take some pictures of the last diff I blew tomorrow, and when I have time to swap this one out, I'll take some pics of the inside of it.

I blew up an open diff in sand once, rpms were too high and spidergears shattered when I got traction. I got home and promptly welded them together never had a problem since. The R160 ring and pinion are usually strong enough to handle anything a subie can throw at it. The spider gears are the weak link. 510 guys run R160s behind turbo VG30's, with the spiders welded of course...